Some users may experience a loss of network access in their Hyper-V guest environments when Symantec Endpoint Protection (SEP) 12.1 with NTP is installed on Hyper-V Host
Due to changes made in the NTP components as of SEP 12.1 RU4 MP1, Hyper-V Guest network activity is handled differently than it was in previous versions.
The issue was addressed in SEP 12.1 RU6. Upgrading to SEP 12.1 RU6 or later will resolve the issue.
In lieu of upgrading to SEP 12.1 RU6, users can workaround this issue by implementing one of the following solutions:
Create an "Allow All" rule in the NTP Firewall rules and place it above the "Block all other IP traffic and log" and "Block all other traffic and don't log" default rules. While this will lower the security of your Firewall policy, the rules above the Allow All rule will still be processed and you will still have the other features of NTP and IPS.
If you are not using NTP, you may simply remove this component from your client installation. This is not recommended as Symantec's best practices recommends all features to be installed on all systems for maximum protection.
Imported Document ID: TECH228599
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